DS3134 datasheet(140/203 Pages) DALLAS

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DS3134

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Bits 8 to 10 / Transmit Done Queue Status Bit Threshold Setting (TDQT0 to TDQT2). These 3 bits

determine when the DMA will set the Transmit DMA Done Queue Write (TDQW) status bit in the Status

000 = set the TDQW status bit after each descriptor write to the Done Queue

001 = set the TDQW status bit after 2 or more descriptors are written to the Done Queue

010 = set the TDQW status bit after 4 or more descriptors are written to the Done Queue

011 = set the TDQW status bit after 8 or more descriptors are written to the Done Queue

100 = set the TDQW status bit after 16 or more descriptors are written to the Done Queue

101 = set the TDQW status bit after 32 or more descriptors are written to the Done Queue

110 = set the TDQW status bit after 64 or more descriptors are written to the Done Queue

111 = set the TDQW status bit after 128 or more descriptors are written to the Done Queue

8.2.5 DMA CHANNEL CONFIGURATION RAM

Onboard the device there is a set of 1536 dwords (6 dwords per channel times 256 channels) that are used

by the Host to configure the DMA and by the DMA to store values locally when it is processing a packet.

Most of the fields within the DMA Configuration RAM are for use by the DMA and the Host will never

write to these fields. The Host is only allowed to write (i.e. configure) to the lower word of dword 1 for

each HDLC channel. The Host configurable fields are denoted with a thick box as shown below.

Transmit DMA Configuration RAM Figure 8.2.5A

dmatcram

msb

lsb

Transmit DMA Configuration RAM

000h

004h

008h

HDLC

Channel

00Ch

010h

014h

HDLC

Channel

256

Fields shown within the thick box

are written by the Host; all other

fields are for usage by the DMA and

can only be read by the Host

Next Descriptor Pointer (16)

Next Priority Pending Descriptor Pointer (16)

Byte Count (13)

Current Packet Data Buffer Address (32)

Start Descriptor Pointer (16)

Last Pending Descriptor Pointer (16)

Next Pending Descriptor Pointer (16)

Next Priority Descriptor Pointer (16)

Last Priority Pending Descriptor Pointer (16)

DQS

unused (16)

EOF CV

PEND

ST(2)

PRI

ST(2)

unused (9)

17D8h

17DCh

17F0h

17F4h

17F8h

17FCh

PPP

un-

used

Next Descriptor Pointer (16)

Next Priority Pending Descriptor Pointer (16)

Byte Count (13)

Current Packet Data Buffer Address (32)

Start Descriptor Pointer (16)

Last Pending Descriptor Pointer (16)

Next Pending Descriptor Pointer (16)

Next Priority Descriptor Pointer (16)

Last Priority Pending Descriptor Pointer (16)

DQS

unused (16)

EOF CV

PEND

ST(2)

PRI

ST(2)

unused (9)

PPP

un-

used

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